Recombinant Human Carboxypeptidase E/CPE Protein, CF

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R&D Systems Recombinant Proteins and Enzymes
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Recombinant Human Carboxypeptidase E/CPE Protein, CF Summary

Product Specifications

>95%, by SDS-PAGE under reducing conditions and visualized by silver stain
Endotoxin Level
<1.0 EU per 1 μg of the protein by the LAL method.
Measured by its ability to cleave a peptide substrate, benzoyl-AR-OH. The product, Arg, is reacted with ortho-phthaldialdehyde (OPA) to form a fluorescent molecule. The specific activity is >12,000 pmol/min/µg, as measured under the described conditions.
Mouse myeloma cell line, NS0-derived human Carboxypeptidase E/CPE protein
Arg42-Ser453, with a C-terminal 6-His tag
Accession #
N-terminal Sequence
Structure / Form
Mature form
Predicted Molecular Mass
47 kDa
57 kDa, reducing conditions

Product Datasheets

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Carrier Free

What does CF mean?

CF stands for Carrier Free (CF). We typically add Bovine Serum Albumin (BSA) as a carrier protein to our recombinant proteins. Adding a carrier protein enhances protein stability, increases shelf-life, and allows the recombinant protein to be stored at a more dilute concentration. The carrier free version does not contain BSA.

What formulation is right for me?

In general, we advise purchasing the recombinant protein with BSA for use in cell or tissue culture, or as an ELISA standard. In contrast, the carrier free protein is recommended for applications, in which the presence of BSA could interfere.


Formulation Supplied as a 0.2 μm filtered solution in MES and NaCl.
Shipping The product is shipped with dry ice or equivalent. Upon receipt, store it immediately at the temperature recommended below.
Stability & Storage: Use a manual defrost freezer and avoid repeated freeze-thaw cycles.
  • 6 months from date of receipt, -20 to -70 °C as supplied.
  • 3 months, -20 to -70 °C under sterile conditions after opening.

Assay Procedure

  • Assay Buffer: 50 mM NaOAc, 5 µM ZnCl2, pH 5.5
  • Recombinant Human Carboxypeptidase E/CPE (rhCPE) (Catalog # 3587-ZN)
  • Substrate: Benzoyl-Ala-Arg-OH (Bachem, Catalog # G-4145), 50 mM stock in DMSO
  • ortho-phthaldialdehyde (OPA) (134.13 g/mol) (Sigma, Catalog # P0657), 50 mg/mL stock in DMSO
  • OPA Buffer: 0.2 M NaOH containing 0.1% mercaptoethanol (v/v)
  • F16 Black Maxisorp Plate (Nunc, Catalog # 475515)
  • Fluorescent Plate Reader (Model: SpectraMax Gemini EM by Molecular Devices) or equivalent
  1. Dilute rhCPE to 0.1 ng/µL in Assay Buffer.
  2. Dilute Substrate to 1 mM in Assay Buffer.
  3. Combine 75 µL of 0.1 ng/μL rhCPE and 75 µL of 1 mM Substrate. Include a Blank containing 75 µL of Substrate only.
  4. Incubate for 10 minutes at room temperature.
  5. Add 150 µL of 15 mM OPA in 0.2 M NaOH containing 0.1% mercaptoethanol (v/v) to reaction vials and the Blank (stops reaction).
  6. After stopping the reaction, add 75 µL of 0.1 ng/µL rhCPE to the Blank.
  7. Mix well and incubate at room temperature for 2-10 minutes.
  8. Load 200 µL of sample(s) and blank into plate.
  9. Read at excitation and emission wavelengths of 330 nm and 450 nm (top read), respectively in endpoint mode.
  10. Calculate specific activity:

     Specific Activity (pmol/min/µg) =

Adjusted Fluorescence* (RFU) x Conversion Factor** (pmol/RFU)
Incubation time (min) x amount of enzyme (µg)

     *Adjusted for Substrate Blank
     **Derived using calibration standard L-Arginine (Sigma, Catalog # A-5006).

Per Well:
  • rhCPE: 0.005 µg
  • Substrate: 0.25 mM
  • OPA: 7.5 mM
Reconstitution Calculator

Reconstitution Calculator

The reconstitution calculator allows you to quickly calculate the volume of a reagent to reconstitute your vial. Simply enter the mass of reagent and the target concentration and the calculator will determine the rest.


Background: Carboxypeptidase E/CPE

Encoded by the CPE gene and also known as Carboxypeptidase H, CPE is a single chain peptidase with an optimal pH range between 5.0‑6.0. It is a zinc metallocarboxypeptidase that removes basic amino acids from the C-terminus of peptides (1). Like other metallocarboxypeptidases, its activity is stimulated by millimolar concentrations of Co2+. Its activity is regulated by pH-induced aggregation above pH 6.0. Its major function seems to process numerous peptide hormones and neurotransmitters. In addition to its proteolytic function, it also plays a role as a sorting receptor (2), which may be attributed to the sorting of this protein into the secretory pathway. The C-terminal domain of CPE causes the peripheral association of CPE with membranes below neutral pH, resulting in the association of this protein into membranes (3). CPE knockout mice live but become obese due to impaired glucose clearance and insulin resistance (4).

  1. Fricker, L.D. (2004) in Handbook of Proteolytic Enzymes, Barrett, A.J. et al. eds., pp. 840.
  2. Cool, D.R. et al. (1997) Cell 88:73.
  3. Zhang, C-F. et al.  (2003) Biochem. J. 369:453.
  4. Cawley, N.X. et al. (2004) Endocrinology 145:5807.
Entrez Gene IDs
1363 (Human); 12876 (Mouse); 25669 (Rat)
Alternate Names
Carboxypeptidase E; Carboxypeptidase H; CPE; CPH; CPH-1; EC 3.4.17; EC; Enkephalin convertase; Prohormone-processing carboxypeptidase

Citation for Recombinant Human Carboxypeptidase E/CPE Protein, CF

R&D Systems personnel manually curate a database that contains references using R&D Systems products. The data collected includes not only links to publications in PubMed, but also provides information about sample types, species, and experimental conditions.

1 Citation: Showing 1 - 1

  1. Human and monkey lenses cultured with calcium ionophore form alphaB-crystallin lacking the C-terminal lysine, a prominent feature of some human cataracts.
    Authors: Nakajima E, David LL, Riviere MA, Azuma M, Shearer TR
    Invest. Ophthalmol. Vis. Sci., 2009;50(12):5828-36.
    Species: Human
    Sample Types: Buffer
    Applications: Bioassay


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